Some people wrote an Android app that can reset/reload transit tickets using NFC technology. Some of the victims are the SF Muni Ultralight cards and the NJ Path cards. I was in Paris recently and the turnstiles and tickets of the Metro there look exactly the same – maybe they are using the same system?
Pretty cool, but as a New Yorker i would be more interested in seeing some hacks involving the good ol’ MTA Metrocard.